Systems and Methods for Adjusting Movable Lenses in Directional Free-Space Optical Communication Systems for Portable Electronic Devices

ABSTRACT

A directional free-space optical communication system includes a source device including a laser diode and an endpoint device including a photodiode. The endpoint device and the source device also include an adjustable optics subsystem that increases both angular and positional offset tolerance between the source device and the endpoint device.

CROSS REFERENCE TO RELATED APPLICATION

This application is a nonprovisional of and claims the benefit under 35U.S.C. 119(e) of U.S. Provisional Patent Application No. 62/678,215,filed May 30, 2018, and entitled “Systems and Methods for AdjustingMovable Lenses in Directional Free-Space Optical Communication Systemsfor Portable Electronic Devices,” the contents of which is incorporatedby reference as if fully disclosed herein.

FIELD

Embodiments described herein relate to free-space optical communicationsystems and, in particular, to systems and methods for dynamicallyadjusting movable lenses for such systems incorporated into portableelectronic devices.

BACKGROUND

An electronic device can include a free-space optical communicationsystem to wirelessly transmit, receive, or exchange data with anotherelectronic device. In some cases, the optical communication system maybe configured to be directional (e.g., line-of-sight) in order toincrease data transfer rates, to increase data transfer privacy, or forany other suitable purpose.

However, a conventional directional free-space optical communicationsystem is exceptionally dependent on precise alignment of communicatingdevices. As such, conventional free-space optical communication systemscannot be incorporated into portable electronic devices that may bemoved or repositioned from time to time.

SUMMARY

Embodiments described herein reference an apparatus for free-spaceoptical communication in a portable electronic device. The apparatusincludes a photosensitive element coupled to a substrate. In manyembodiments, the photosensitive element includes at least two separatedphotosensitive areas. The apparatus also includes a movable lenspositioned above the photosensitive element. The apparatus additionallyincludes a controller configured to adjust a position of the movablelens based on a power output from a first photosensitive area of thephotosensitive element and a power output from a second photosensitivearea—if any—of the photosensitive element.

Some embodiments described herein reference a method of operating afree-space optical communication system with a source device and anendpoint device, the method including the operations of: changing aposition of a movable lens positioned over a laser diode in the sourcedevice according to a pattern; monitoring power output from aphotosensitive area of a photodiode in the endpoint device for a maximumand, in response, sending a signal to the source device to stop changinga position of the source device lens; changing a position of a secondmovable lens positioned over the photodiode in the endpoint device; andmonitoring power output from a photosensitive area of the photodiode foranother maximum and, in response, stopping movement of the secondmovable lens.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will now be made to representative embodiments illustrated inthe accompanying figures. It should be understood that the followingdescriptions are not intended to limit this disclosure to one includedembodiment. To the contrary, the disclosure provided herein is intendedto cover alternatives, modifications, and equivalents as may be includedwithin the spirit and scope of the described embodiments, and as definedby the appended claims.

FIG. 1A depicts a directional free-space optical communication systemcoupling two electronic devices.

FIG. 1B is a simplified system diagram of the directional free-spaceoptical communication system of FIG. 1A.

FIG. 2A depicts a simplified representation of a source device and anendpoint device, collimated relative to one another.

FIG. 2B depicts the simplified representation of the collimated devicesof FIG. 2A, viewed along line A-A.

FIG. 2C depicts the simplified representation of the collimated devicesof FIG. 2A, viewed along line B-B.

FIG. 2D depicts the simplified representation of the collimated devicesof FIG. 2A, viewed along line C-C.

FIG. 3 depicts a system diagram of a directional free-space opticalcommunication system, such as described herein.

FIG. 4A depicts an endpoint device of a directional free-space opticalcommunication system, such as described herein, including a laterallymovable lens.

FIG. 4B depicts the movable lens of FIG. 4A, shifted in a direction.

FIG. 5A depicts an endpoint device of a directional free-space opticalcommunication system, such as described herein, including an angularlymovable optical subassembly.

FIG. 5B depicts the movable lens of FIG. 5A, tilted in a direction.

FIG. 6A depicts a top view of a photodiode of an endpoint device of adirectional free-space optical communication system, such as describedherein, depicting a beam spot illuminating a central region of aphotosensitive area of the photodiode.

FIG. 6B depicts the photodiode of FIG. 6A, depicting the beam spotshifted in a direction relative to the central region of thephotosensitive area.

FIG. 6C depicts a top view of another photodiode of an endpoint deviceof a directional free-space optical communication system, such asdescribed herein, depicting a beam spot illuminating more than onephotosensitive area of the photodiode.

FIG. 7 depicts a top view of another photodiode of an endpoint device ofa directional free-space optical communication system, such as describedherein, including a segmented photosensitive area and depicting a beamspot illuminating more than one photosensitive area of the photodiode.

FIG. 8 is a simplified flow chart showing example operations of a methodof positioning a movable lens in a directional free-space opticalcommunication system, such as described herein.

FIG. 9 is a simplified flow chart showing example operations of anothermethod of positioning a movable lens in a directional free-space opticalcommunication system, such as described herein.

The use of the same or similar reference numerals in different figuresindicates similar, related, or identical items.

The use of cross-hatching or shading in the accompanying figures isgenerally provided to clarify the boundaries between adjacent elementsand to facilitate legibility of the figures. Accordingly, neither thepresence nor the absence of cross-hatching or shading conveys orindicates any preference or requirement for particular materials,material properties, element proportions, element dimensions,commonalities of similarly illustrated elements, or any othercharacteristic, attribute, or property for any element illustrated inthe accompanying figures.

Similarly, certain accompanying figures include vectors, rays, tracesand/or other visual representations of one or more example paths—whichmay include reflections, refractions, diffractions, and so on, throughone or more mediums—that may be taken by one or more photons originatingfrom one or more light sources shown or, or in some cases, omitted from,the accompanying figures. It is understood that these simplified visualrepresentations of light are provided merely to facilitate anunderstanding of the various embodiments described herein and,accordingly, may not necessarily be presented or illustrated to scale orwith angular precision or accuracy, and, as such, are not intended toindicate any preference or requirement for an illustrated embodiment toreceive, emit, reflect, refract, focus, and/or diffract light at anyparticular illustrated angle, orientation, polarization, color, ordirection, to the exclusion of other embodiments described or referencedherein.

Additionally, it should be understood that the proportions anddimensions (either relative or absolute) of the various features andelements (and collections and groupings thereof) and the boundaries,separations, and positional relationships presented therebetween, areprovided in the accompanying figures merely to facilitate anunderstanding of the various embodiments described herein and,accordingly, may not necessarily be presented or illustrated to scale,and are not intended to indicate any preference or requirement for anillustrated embodiment to the exclusion of embodiments described withreference thereto.

DETAILED DESCRIPTION

Embodiments described herein reference electronic devices configured toreceive data from other electronic devices via free-space opticalcommunication.

As used herein, the phrase “free-space optical communication” refers tothe delivery of digital and/or analog information or data from at leastone “source device” to at least one “endpoint device” by selectivelymodulating and/or otherwise controlling the amplitude, frequency, phase,polarization, angle, pulse width, duty cycle, and/or any other suitablecharacteristic of visible or traditionally non-visible light propagatingthrough a medium (e.g., gases, liquids, vacuum, and so on) thatphysically separates the source device(s) from the endpoint device(s).

Any stationary or portable electronic device can be either (or both) asource device or an endpoint device of a free-space opticalcommunication system, such as described herein. Example electronicdevices include, but are not limited to: mobile phone devices; tabletdevices; laptop devices; desktop computers; computing accessories;peripheral input devices; home or business networking devices; aerial,marine, submarine, or terrestrial vehicle control devices or networkingdevices; mobile entertainment devices; augmented reality devices;virtual reality devices; industrial control devices; digital walletdevices; home or business security devices; wearable devices; health ormedical devices; implantable devices; clothing-embedded devices; fashionaccessory devices; home or industrial appliances; media appliances; andso on.

In some embodiments, a free-space optical communication system is“directional” in that focused light or laser light emitted from thesource device(s) propagates through a medium between the sourcedevice(s) and the endpoint device(s) along a substantially line-of-sightpath. A directional free-space optical communication system canfacilitate increased data transfer rates (e.g., tens of gigabits persecond to terabits per second), increased data transfer privacy, andincreased data transfer security relative to conventionaldevice-to-device data communication protocols, such as Wi-Fi, Near-FieldCommunications, or Bluetooth.

As noted above, a directional free-space optical communication system,such as described herein, includes at least a source device and at leastone endpoint device. The source device includes at least one focusedlight source or laser light source and the endpoint device includes atleast one photosensitive element. When light emitted from the laserlight source of the source device is collimated (e.g., emitted withminimal or negligible beam divergence or convergence) and thephotosensitive element of the endpoint device is positioned to acceptthe collimated light (e.g., the source device and the endpoint deviceare precisely aligned) a signal applied to modulate the laser lightsource can be received at the photosensitive element without substantiallosses. In other words, the signal received by the photosensitiveelement can be characterized by a high signal-to-noise ratio that canfacilitate a high data transfer rate from the source device to theendpoint device. In this configuration and alignment, the source deviceand the endpoint device can be described as “optically coupled.” It maybe appreciated that, in many embodiments, optically coupled devices caneach include one or more light sources and one or more photosensitiveelements to enable multi-channel and/or two-way communication and/ormulti-device communication (e.g., three or more devices opticallycoupled). However, for simplicity of description, the embodiments thatfollow reference a directional free-space optical communication systemconfigured for one-way, single-channel, data transfer from a sourcedevice to an endpoint device.

In this example, the light source of the source device can be anysuitable electrical or electronic light source or combination of lightsources, including both multipart and solid-state light sources. In manyembodiments, a light source of a source device is a semiconductor lightsource such as, but not limited to: a vertical-cavity surface-emittinglaser (a “VCSEL”); a vertical external-cavity surface-emitting laser; alight-emitting diode; an organic light-emitting diode; a resonant-cavitylight-emitting diode; a micro-scale light-emitting diode; asuperluminescent light-emitting diode; a broad-area laser diode; adiode-pumped laser; a mode-locked diode laser; an infrared band laser;an ultraviolet band laser; and so on.

In some embodiments, the light source of a source device can beoptically coupled to one or more passive or active optical structuresthat direct, collimate, and/or focus light emitted from the light sourcein a particular direction or manner. Example optical structures caninclude, but may not be limited to: optical adapters; waveguides;optical fibers; reflectors; lenses; microlenses; beamforming and/orbeam-directing lenses or lens structures; beam splitters; beamcollimators; polarizers; movable lenses; color filters; cut filters;beam expanders; beam divergers; planar light wave circuits; and so on.

The photosensitive element of an endpoint device, such as describedherein, can be any suitable photosensitive element or combination ofelements, including both multipart and solid-state photosensitiveelements operated in either photovoltaic mode (e.g., not reverse biased)or photoconductive mode (e.g., reverse biased). Example photosensitiveelements include, but are not limited to: semiconductor photodiodes;semiconductor photodetectors; avalanche diodes; charge-coupled devices;and so on. Further, it may be appreciated that the size and shape of aphotosensitive element can vary from embodiment to embodiment. In somecases, a “photosensitive area” of a photosensitive element can take acircular shape, whereas in other cases, the photosensitive area can takeanother shape (e.g., square, rectangular, octagonal, irregular,polygonal, and so on). Further, some embodiments can include more thanone photosensitive area. For example, a first photosensitive area can beinset within a second photosensitive area of the same photosensitiveelement. In these examples, different photosensitive areas may be formedfrom different materials, or material combinations, and/or may havedifferent photosensitivity or electrical characteristics (e.g.,responsivity, rise time, fall time, reverse bias, dark current, and soon). In further examples, a photosensitive element can be constructedsuch that its photosensitive area exhibits particular electricalproperties, at least in part, as a result of the materials, geometry, ordimensions of the photosensitive area. For example, it may beappreciated that different semiconductor materials (e.g., silicon,germanium, indium-gallium arsenide, gallium phosphide, and so on) mayexhibit different electrical properties (e.g., responsivity, rise time,fall time, dark current, and so on) in response to stimulation bydifferent spectral ranges and/or amplitudes of light. Similarly,different photosensitive area geometries and/or dimensions may result indifferent electrical properties. For example, smaller photosensitiveareas may be associated with faster rise times and faster fall times.

As with the light source of the source device, in some embodiments, thephotosensitive element of an endpoint device can be optically coupled toone or more passive or active optical structures that redirect and/orfocus light onto the photosensitive area of the photosensitive element.Example optical structures can include, but may not be limited to:optical adapters; optical fibers; reflectors; lenses; microlenses;beamforming and/or beam-directing lenses or lens structures; beamcollimators; polarizers; movable lenses; color filters; cut filters;beam concentrators; planar light wave circuits; and so on.

For simplicity of description, the embodiments that follow reference asource device including at least one VCSEL light source (hereinafter, a“laser” or “laser diode”) that emits light in a spectral range includinga traditionally non-visible frequency band (e.g., infrared light).Further, although not required for all embodiments, the example VCSELlight source described in reference to many embodiments that follow ispresumed to be a Class 1 laser as defined by the American NationalStandards Association.

Similarly, for simplicity of description, the embodiments that followreference an endpoint device including at least one semiconductorphotodiode (hereinafter, a “photodiode”). The photodiode has a generallysmall, circular photosensitive area (e.g., having a diameter of lessthan 100 μm, such as 20-50 μm) and is operated in a photoconductivemode. The photosensitive area of this example photodiode is responsiveto light in the spectral range emitted by the laser diode of the sourcedevice.

As noted above, a directional free-space optical communication system,such as described herein, preferably operates when the source device andthe endpoint device are precisely aligned such that a considerablequantity (which may vary from embodiment to embodiment) of laser lightemitted from the laser diode of the source device illuminates thephotodiode of the endpoint device. Conversely, if the source device andthe endpoint device are not precisely aligned, partial or total signalloss can occur because the laser diode may not effectively illuminatethe photodiode.

To account for positional and/or angular offset(s) between the sourcedevice and the endpoint device—or, more generally, between the laserdiode and the photodiode—many embodiments described herein referenceoptical structures for either or both the source device and the endpointdevice that increase positional and/or angular offset tolerance.

For example, in one embodiment, an endpoint device of a directionalfree-space optical communication system can include an adjustable opticssubsystem. In one example, the adjustable optics subsystem includes amovable lens positioned over the photodiode of the endpoint device. Inother embodiments, the adjustable optics subsystem includes a movablereflective surface (e.g., mirror) positioned adjacent to the photodiodeof the endpoint device. The movable reflective surface may be a flatsurface or, in other embodiments, it may be curved (e.g., concave orconvex, or any other suitable curvature). For simplicity of description,the embodiments that follow generally reference an adjustable opticssubsystem including a single movable lens, but it may be appreciatedthat this is merely one example; other embodiments can include more thanone movable lens, a movable reflective surface, multiple movablereflective surfaces, and/or a combination of movable lenses andreflective surfaces.

Continuing the example introduced above, an adjustable optics subsystem,such as described herein, can adjust a position of a movable lens inorder to direct and/or otherwise focus laser light emitted from a laserdiode of a source device onto a photosensitive area of a photodiode inthe endpoint device. In this manner, positional and angular offsettolerance of the directional free-space optical communication system isincreased.

In some embodiments, an adjustable optics subsystem in an endpointdevice can adjust the position of a movable lens based on an output of aphotodiode in the endpoint device. For example, if power output from thephotodiode is less than a threshold value, the adjustable opticssubsystem can cause the movable lens to shift in a selected direction.If power output from the photodiode either decreases or does not changein response to the movement, the adjustable optics subsystem may movethe movable lens in another, different, direction until an increase inoutput power (optionally beyond a threshold, which may be different thanthe first threshold) is achieved.

In some cases, the adjustable optics subsystem can iterate through anumber of predetermined and/or predefined positions in order to find anoptimal position for the movable lens at which power output from thephotodiode is a maximum. In other embodiments, the adjustable opticssubsystem can cause the movable lens to follow a predetermined pathrelative to the photosensitive area of the photodiode (e.g., serpentinepath, spiral path, and so on) in order to find an optimal position orset of positions for the movable lens at which power output from thephotodiode is a maximum. In other cases, other characteristics of outputfrom the photodiode can be used such as, but not limited to: frequencycontent; absolute value; voltage; current; and so on. In these andsimilar examples, the movable lens can be moved to one or morepredefined positions. For each predefined position of the movable lens,one or more output characteristics from the photodiode can be obtained.Thereafter, a spatial and/or angular profile or map—corresponding to, inone example, intensity of light received by the photodiode at differentpositions of the movable lens—can be extrapolated and/or otherwiseformed from the one or more output characteristics associated with theone or more predefined positions of the movable lens. Thereafter, themovable lens can be moved to a predefined position or another positionbased on the spatial and/or angular profile or map.

In other cases, the adjustable optics subsystem can adjust the positionof the movable lens based on output from one or more sensors within (orin communication with) the endpoint device. For example, in some cases,an endpoint device can include an accelerometer, a gyroscope,magnetoresistance sensor, a magnetometer, or any other suitable sensor.In this example, the adjustable optics subsystem can adjust the positionof the movable lens (or a position of more than one movable lens or, insome embodiments, an angle of a reflective surface adjacent to thephotodiode) based on output from one or more of the accelerometer,gyroscope, magnetoresistance sensor, or magnetometer.

In still further examples, the adjustable optics subsystem can adjustthe position of the movable lens based on user input. For example, auser of an endpoint device may provide input corresponding to adirection of a source device. In response to receiving user input, theadjustable optics subsystem can adjust the position of the movable lensin the direction (or in the opposite direction) indicated by the user.For example, in some cases, an endpoint device may be configured tooptically couple to more than one source device. In these cases, userinput may be provided so that the adjustable optics subsystem moves themovable lens in order to optically couple the endpoint device to aspecific or user-selected source device.

In still further examples, the adjustable optics subsystem can adjustthe position of the movable lens based on, without limitation: an outputfrom one or more optimization algorithms; feedback from another element,system or subsystem of the endpoint device; and so on. It may beappreciated that an adjustable optics subsystem such as described hereincan utilize any suitable or appropriate technique, or combination oftechniques, to adjust and/or set the position of a movable lens or amovable reflective surface.

In some embodiments, a source device can also include an adjustableoptics subsystem. For example, the adjustable optics subsystem in asource device can include a movable lens (and/or movable reflectivesurface) positioned over the laser diode. In this embodiment, theadjustable optics subsystem can adjust a position of the movable lens,biasing the movable lens in one or more directions, in order to directand/or otherwise focus laser light emitted from the laser diode towardan endpoint device. The adjustable optics subsystem of a source devicecan be configured in the same manner as described above in reference tothe example endpoint device.

In certain further embodiments, a source device can include a firstadjustable optics subsystem and an endpoint device can include a secondadjustable optics subsystem. In this example, the first adjustableoptics subsystem can be used to direct laser light emitted from thelaser diode in the source device toward the endpoint device. Similarly,the second adjustable optics subsystem can be used to focus laser lightreceived from the source device onto the photosensitive area of thephotodiode of the endpoint device. In this manner, the first adjustableoptics subsystem and the second adjustable optics subsystem cancooperate to direct laser light emitted from the laser diode onto thephotosensitive area of the photodiode of the endpoint device. In furtherembodiments, the first adjustable optics subsystem and the secondadjustable optics subsystem can communicate with one another in order tomore quickly and/or more accurately focus laser light emitted from thelaser diode onto the photosensitive area of the photodiode. For example,the source device can encode information regarding the position of themovable lens of the first adjustable optics subsystem into the laserlight emitted by the laser diode. In this example, the endpoint devicecan use the information regarding the position of the movable lens ofthe first adjustable optics subsystem to adjust the position of themovable lens of the second adjustable optics subsystem. In other cases,a position of the movable lens of the first adjustable optics subsystemcan be communicated to the second adjustable optics subsystem via anauxiliary or secondary communication channel or protocol, such as viaWi-Fi, Bluetooth, Near-Field Communications, Infrared, or Ethernetprotocols. One may appreciate that these are merely examples; in otherembodiments, a position of the movable lens of the first adjustableoptics subsystem can be communicated to the second adjustable opticssubsystem using any other suitable technique. In some furtherembodiments, relative positions of the movable lenses of the first andsecond adjustable optics subsystems can be used to determine an angleand/or positional offset between a source device and an endpoint device.

These foregoing and other embodiments are discussed below with referenceto FIGS. 1A-9. However, those skilled in the art will readily appreciatethat the detailed description given herein with respect to these figuresis for explanatory purposes only and should not be construed aslimiting.

FIG. 1A depicts a directional free-space optical communication system100 communicably and optically coupling two electronic devices,identified as the source device 102 and the endpoint device 104. In theillustrated example, the source device 102 and the endpoint device 104are separated by an air gap 106 (e.g., free space). In typical examples,the source device 102 and the endpoint device 104 are battery-operatedportable electronic devices, but this may not be required; in someembodiments, one or both of the source device 102 and the endpointdevice 104 are substantially stationary.

As noted above, the source device 102 and the endpoint device 104 can beany suitable electronic devices; example electronic devices arenon-exhaustively listed above. The source device 102 includes a housing108 enclosing, at least in part, an optical communication module 110that includes a laser diode. Similarly, the endpoint device 104 includesa housing 112 enclosing, at least in part, an optical communicationmodule 114 that includes a photodiode. In some cases, such asillustrated, the optical communication module 110 can extend at leastpartially through the housing 108, although this is not required. Insome cases, a protective cover (e.g., lens window) can be provided inthe housing 108. In these embodiments, the optical communication module110 is positioned behind the protective cover. The optical communicationmodule 114 can be similarly configured in the housing 112.

As noted with respect to other embodiments described herein, the sourcedevice 102 and the endpoint device 104 can be configured formulti-channel and/or two-way communication. In these examples, theoptical communication module 110 of the source device 102 includes atleast one photodiode and the optical communication module 114 of theendpoint device 104 includes at least one laser diode. For simplicity ofdescription, one-way, single-channel communication from the sourcedevice 102 to the endpoint device 104 is described below.

The laser diode of the optical communication module 110 of the sourcedevice 102 emits a beam of light u₁ across the air gap 106 toward thephotodiode of the optical communication module 114 of the endpointdevice 104. As noted above, by modulating one or more characteristics ofthe beam of light u₁, the source device 102 can communicate digitaland/or analog information to the endpoint device 104 (hereinafterreferred to as, simply, “data” communicated from a source device to anendpoint device). Example beam characteristics that can be modulated bythe source device 102 to communicate data to the endpoint device 104 arenon-exhaustively listed above.

In some examples, data communicated by the source device 102 to theendpoint device 104 can be encoded according to a particular schema(e.g., code division; time division; quadrature modulation; phase shiftkeying; frequency-shift keying; amplitude-shift keying; pulse codemodulation; and so on) and/or may be encrypted. In other examples, thedata communicated by the source device 102 to the endpoint device 104can conform to a particular data transfer protocol—whether proprietaryor standardized—such as, but not limited to: universal serial bus(typically referred to as “USB”); peripheral component interconnectexpress standard (typically referred to as “PCIe”); controller areanetwork (typically referred to as “CAN”); on-board diagnostics(typically referred to as “ODB” or “ODB-II”); serial peripheralinterface bus (typically referred to as “SPI Bus”); high-definitionmultimedia interface (typically referred to as “HDMI”); Ethernet;integrated drive electronics (typically referred to as “IDE”); serial orparallel advanced technology attachment (typically referred to as “SATA”or “PATA”); inter-integrated circuit bus (typically referred to as“I2C”); and so on. In other cases, more than one protocol, encoding,and/or encryption technique or technology can be used in parallel.

The data communicated by the source device 102 to the endpoint device104 can be any suitable data or data type including but not limited to:real-time data; data streams; data files; configuration files;encryption keys; messages; media files or streams; local or remotenetwork resources or addresses; synchronization data; firmware;software; networking data; human interface device and/or sensor datastreams or configurations; and so on. In other cases, data communicatedby the source device 102 to the endpoint device 104 can be associatedwith a secure shell or other remote login session. In other cases, datacommunicated by the source device 102 to the endpoint device 104 can beassociated with a serial data link or serial connection between thesource device 102 and the endpoint device 104. In still furtherexamples, other data or data types—or combinations of data or datatypes—can be communicated from the source device 102 to the endpointdevice 104.

It may be appreciated that the foregoing description of FIG. 1A, and thevarious alternatives thereof and variations thereto are presented,generally, for purposes of explanation, and to facilitate a thoroughunderstanding of various possible configurations of a directionalfree-space optical communication system, such as described herein.However, it will be apparent to one skilled in the art that some of thespecific details presented herein may not be required in order topractice a particular described embodiment, or an equivalent thereof.For simplicity of description and illustration, FIG. 1B is provided.This figure depicts a simplified block diagram of the source device 102and the endpoint device 104 of FIG. 1A, showing various operationaland/or structural components that can be included in certainembodiments.

FIG. 1B depicts a simplified system diagram of the directionalfree-space optical communication system 100 of FIG. 1A. As shown in thefigure, the source device 102 includes a laser diode 116 that emits thebeam of light u₁ toward the endpoint device 104 in order to illuminate aphotodiode 118 to communicate data to the endpoint device 104.

The source device 102 can (optionally) include an optical structure 120to adjust one or more characteristics of the beam of light u₁ as itexits the source device 102. As noted above, the optical structure 120can be configured to move a movable lens to direct the beam of light u₁toward the endpoint device 104 in order to accommodate a greater rangeof positional and/or angular offset(s) of the endpoint device 104 (see,e.g., FIGS. 2A-3).

Similarly, the endpoint device 104 can (optionally) include an opticalstructure 122 to adjust one or more characteristics—such as adirection—of the beam of light u₁ before the beam of light u₁illuminates the photodiode 118. Example characteristics of a beam oflight that can be modified by an optical structure, such as describedherein, are non-exhaustively provided above. Non-exhaustive exampleoptical structures that can be included in a source device are describedbelow in reference to FIG. 3. Non-exhaustive example optical structuresthat can be included in an endpoint device are described below inreference to FIGS. 3-5B.

The laser diode 116 of the source device 102 is coupled to a drivecircuit, identified as the drive circuit 124. The drive circuit 124 canbe any suitable analog or digital circuit or purpose-configuredprocessor, or combination thereof configured to generate direct currentand/or alternating current signals suitable to drive the laser diode 116to emit laser light. The drive circuit 124 is typically configured tocontrol a level of current circulated through the laser diode 116,although this may not be required; other embodiments may control avoltage applied across the laser diode 116. The drive circuit 124 canapply any suitable current or voltage waveform to cause the laser diode116 to emit laser light in any suitable manner (e.g., pulse width, dutycycle, color, frequency, amplitude, and so on). The laser light may bemonochromatic or polychromatic. The laser diode 116 may be a single modeor a multi-mode laser. As may be appreciated, the waveform applied tothe laser diode 116 corresponds to the data to be communicated from thesource device 102 to the endpoint device 104 and will accordingly varyfrom embodiment to embodiment and will be based on the content of thedata to be communicated.

The source device 102 can also include other components, including aprocessor 126, a memory 128, a display 130, an input/output system 132,an adjustable optics subsystem 134, and so on.

In many configurations, the processor 126 of the source device 102 canbe configured to access and execute instructions stored in the memory128 in order to instantiate any number of suitable classes, objects,virtual machines, threads, pipelines, and/or routines to perform,monitor, and/or coordinate one or more operations of the source device102. Further, the processor 126 can be communicably coupled—eitherdirectly (e.g., via general-purpose input/output pins) or indirectly(e.g., via an intermediary circuit or integrated circuit)—to each of thehardware components of the source device 102, including the display 130,the input/output system 132, the adjustable optics subsystem 134, andthe drive circuit 124. In this manner, the processor 126 can coordinatethe operation of the various hardware components of the source device102.

As one example, the processor 126 can cause the display 130 to render auser interface while monitoring a user input sensor (e.g., capacitivetouch sensor, capacitive force sensor, and so on) of the input/outputsystem 132 to detect one or more characteristics of a user's physicalinteraction with the display 130. As a result of this construction, auser of the source device 102 is encouraged to interact with contentshown on the display 130.

The adjustable optics subsystem 134 of the source device 102 can beconfigured in a number of ways. In typical implementations, theadjustable optics subsystem 134 includes at least one processor,generally referred to as a controller. The controller of the adjustableoptics subsystem 134 is communicably coupled to an actuation mechanism(not shown) configured to move a movable lens of the optical structure120.

In these embodiments, the controller of the adjustable optics subsystem134 causes the actuation mechanism to move the movable lens in anysuitable direction by any suitable amount. As noted with respect toother embodiments described herein, the controller may be configured tocause the actuation mechanism to move the moveable lens in order todirect laser light emitted from the laser diode 116 in a particulardirection, such as toward the endpoint device 104.

In some embodiments, the actuation mechanism of the adjustable opticssubsystem 134 is configured to move and/or shift the movable lens of theoptical structure 120 in a single, linear direction (e.g., a singledegree of freedom). In other cases, the actuation mechanism isconfigured to move the movable lens in more than one linear direction(e.g., multiple degrees of freedom). In still further embodiments, theactuation mechanism of the adjustable optics subsystem 134 is configuredto move and/or shift the movable lens in a vertical direction, relativeto the laser diode 116. In still further embodiments, the actuationmechanism of the adjustable optics subsystem 134 is configured to tiltthe movable lens to an angle relative to an exterior surface of thelaser diode 116. In some embodiments, the actuation mechanism can beconfigured to tilt, move, and/or shift the movable lens.

It may be appreciated that the actuation mechanism of the adjustableoptics subsystem 134 can vary from embodiment to embodiment. In oneexample, the actuation mechanism is magnetically controlled. Morespecifically, the actuation mechanism includes an electromagnetpositioned along an axis of the movable lens of the optical structure120. The actuation mechanism also includes a permanent magnet (or secondelectromagnet) coupled to the movable lens and aligned with theelectromagnet. The actuation mechanism also includes a centering elementformed from an elastic material or structure, such as a spring or anelastomer. The centering element supports the movable lens and exerts arestoring force to re-center the movable lens over the laser diode 116when the actuation mechanism is not activated.

As a result of this construction, the controller of the adjustableoptics subsystem 134 can apply a current to the electromagnet in orderto attract or repel the permanent magnet (and thus the movable lens) bya certain amount proportional and/or related to both the magnitude ofcurrent applied and the restoring force applied by the centeringelement. As such, by varying the amount of current applied to theelectromagnet, the controller of the adjustable optics subsystem 134 canprecisely control the position of the movable lens along the axis of themovable lens with which the electromagnet is aligned.

In a further implementation of this example, the adjustable opticssubsystem 134 can include two or more electromagnets, each associatedwith, and aligned with, a respective permanent magnet (or secondaryelectromagnets) coupled to the movable lens of the optical structure120. In this embodiment, the controller of the adjustable opticssubsystem 134 can precisely control the position of the movable lensalong multiple axes. In one embodiment, the adjustable optics subsystem134 includes two magnetically controlled actuation mechanisms that arepositioned ninety degrees offset from one another. In thisconfiguration, one of the two actuation mechanisms can control movementof the movable lens in an “X” direction, whereas the other actuationmechanism can control movement of the movable lens in a “Y” direction.

In other embodiments, the actuation mechanism may be implementeddifferently. Suitable actuation mechanisms include, but are not limitedto: piezoelectric actuation mechanisms; magnetostrictive mechanisms;mechanisms implemented with electroactive polymers; mechanismsimplemented with shape-memory wire; and so on. For simplicity ofdescription, the embodiments that follow generally reference anadjustable optics subsystem that includes a magnetically controlledactuation mechanism, but it is appreciated that this is merely oneexample.

Returning to the endpoint device 104 depicted in FIG. 1B, the photodiode118 is coupled to amplifier 136. In many embodiments, the amplifier 136is a transimpedance amplifier, but this may not be required of allembodiments. As with the drive circuit 124 of the source device 102, theamplifier 136 can be any suitable analog or digital circuit orpurpose-configured processor, or combination thereof. The amplifier 136is typically configured to convert a level of current circulated throughthe photodiode 118 to a corresponding level of voltage, although thismay not be required.

In some examples, the amplifier 136 is coupled to a multi-bitanalog-to-digital converter (not shown) to quantize the level of voltageoutput from the amplifier 136 into a series of digitally representedvalues.

In other cases, the amplifier 136 can be coupled to a single-bitanalog-to-digital converter or a limiting amplifier configured togenerate a sequence of voltages that correspond to digital data (e.g.,ones and zeros). In other words, an output of the amplifier 136 can becoupled to an input (e.g., a gate) of a high-speed switching element(e.g., diode, transistor, and so) in order to quantize the voltageoutput from the amplifier 136 as either a binary one or a binary zero.

In still other examples, the amplifier 136 can be coupled to a bufferand/or shift register configured to convert serial information receivedfrom the source device into a parallel data.

In still further examples, the output from amplifier 136 can be provideddirectly (with or without a resistor or other elements in series, suchas a high-pass filter) to an input of a digital circuit for furtherprocessing. As may be appreciated, the waveform output from thephotodiode 118 corresponds to the data to be communicated from thesource device 102 to the endpoint device 104 and will accordingly varyfrom embodiment to embodiment and will be based on the content of thedata communicated to the endpoint device 104.

Similar to the source device 102 described above, the endpoint device104 can also include other components, including a processor 138, amemory 140, a display 142, an input/output system 144, an adjustableoptics subsystem 146, and so on.

Similar to the processor 126 of the source device 102 described above,in many configurations, the processor 138 of the endpoint device 104 canbe configured to access and execute instructions stored in the memory140 in order to instantiate any number of suitable classes, objects,virtual machines, threads, pipelines, and/or routines to perform,monitor, and/or coordinate one or more operations of the endpoint device104. Further, the processor 138 can be communicably coupled—eitherdirectly (e.g., via general-purpose input/output pins) or indirectly(e.g., via an intermediary circuit or integrated circuit)—to each of thehardware components of the endpoint device 104, including the display142, the input/output system 144, the adjustable optics subsystem 146,and the amplifier 136. In this manner, the processor 138 can coordinatethe operation of the various hardware components of the endpoint device104 in a manner similar to that described above in reference to theprocessor 126 of the source device 102.

Similarly, it may be appreciated that the adjustable optics subsystem146 can be appropriately configured in the same manner as the adjustableoptics subsystem 134 described above. Namely, it is understood that theadjustable optics subsystem 146 can include a controller and anactuation mechanism configured to cooperate to move a movable lensassociated with the optical structure 122.

Accordingly, generally and broadly in view of FIGS. 1A-1B, it isunderstood that a directional free-space optical communication systemcan be configured in a number of ways. For example, as noted above,certain electronic devices can operate as both a source device and anendpoint device. In this manner, two-way optical communication can beachieved. Further, in certain embodiments, a source device can includemore than one laser diode and an endpoint device can include more thanone photodiode. In this manner, multi-channel optical communication canbe achieved.

Further, although the illustrations of FIG. 1A-1B depict opticalcommunication modules as purpose-configured components, this may not berequired. For example, in some embodiments, a display or other lightsource of a source device can be used to transmit data using thetechniques and methods described herein. Similarly, a camera or aproximity sensor of an endpoint device can be used to receive data usingthe techniques and methods described herein.

Further, it is appreciated that the specific configuration(s) shown inFIGS. 1A-1B are not required. In other cases, a laser diode of a sourcedevice and/or a photodiode of an endpoint device can be disposed inportions of an electronic device housing different from the positionsshown.

Additionally, it may be appreciated that other components and/or systemsmay be included in particular embodiments. For example, as noted above,in some examples, light emitted from a laser diode of a source devicecan be configured to conform to a standardized data transfer protocol,such as PCIe. In these embodiments, the endpoint device may include oneor more circuits, processors, or components configured to route theinformation received from the source device directly to a component orsubsystem of the endpoint device that responds to the standardizedprotocol. In this manner, a processor in the source device can directlyaccess and/or control a resource of the endpoint device via thedirectional free-space optical communication system.

Thus, it is understood that the foregoing descriptions of specificembodiments are presented for the purposes of illustration anddescription. These descriptions are not exhaustive nor intended to limitthe disclosure to the precise forms recited herein. To the contrary, itwill be apparent to one of ordinary skill in the art that manymodifications and variations are possible in view of the aboveteachings.

For example, in many embodiments, alignment between a source device andan endpoint device in the collimated regime may not be guaranteed. FIGS.2A-2D depict a simplified representation of a directional free-spaceoptical communication system 200 in which a source device 202 and anendpoint device 204 are movable and separated by an air gap 206. As withother embodiments described herein, a beam of light u₁ emitted from alaser diode in the source device 202 propagates through the air gap 206along a line-of-sight path toward the endpoint device 204 to illuminatea photodiode in the endpoint device 204.

In many cases, the endpoint device 204 may be movable relative to thesource device 202. In the illustrated embodiment, six axes of potentialmovement are shown including three translational axes and threerotational axes. More specifically, the endpoint device 204 canmove—relative to the source device 202—in three-dimensional space in anX-direction (e.g., to the left or to the right of the source device 202;see, e.g., FIG. 2B), in a Y-direction (e.g., toward or away from thesource device 202; see, e.g., FIG. 2C), and/or in a Z-direction (e.g.,above or below the source device 202; see, e.g., FIG. 2D). Similarly,the endpoint device 204 can rotate about the Y-direction axis to anangle Φ (e.g., roll; see, e.g., FIG. 2D), about the X-direction axis toan angle Θ (e.g., pitch; see, e.g., FIG. 2C), and/or about theZ-direction axis to an angle Ψ (e.g., yaw; see, e.g., FIG. 2B).

To account for variations in alignment between a source device and anendpoint device of a directional free-space optical communicationsystem, many embodiments optically couple one or more passive or activeoptical structures or elements—such as reflectors, lenses, waveguides,adjustable optics subsystems, and so on—to either or both the laserdiode in a source device or the photodiode in an endpoint device.

FIG. 3 depicts a system diagram of a directional free-space opticalcommunication system 300. As with other embodiments described herein,the system includes a source device 302 and an endpoint device 304 thatare separated by an air gap 306. The source device 302 includes a laserdiode 308 and the endpoint device 304 includes a photodiode 310. Thelaser light output from the laser diode 308 is modulated and/orotherwise controlled according to a selected data signal or waveform bya drive circuit 312. In the endpoint device 304, the photodiode 310 iselectrically coupled to an amplifier 314 that may be a transimpedanceamplifier configured to convert current output from the photodiode 310into a variable voltage. In some embodiments, the amplifier 314 alsoprovides a reverse bias to the photodiode 310 so that the photodiode 310operates in a photoconductive mode and not a photovoltaic mode.

In many embodiments, the drive circuit 312 of the source device 302 isformed onto a semiconductor substrate that provides both mechanicalsupport and electrical connection to the laser diode 308. The drivecircuit 312 of the source device 302 can be implemented and/orfabricated in a number of suitable ways. In some examples, the drivecircuit 312 and the laser diode 308 are fabricated in the same processor operation, but this may not be required. In some embodiments, thedrive circuit 312 may be positioned off-board from a rigid substrate orflexible circuit board to which the laser diode 308 is coupled. It maybe appreciated that the simplified layout shown in FIG. 3 is merely oneexample and that many other implementations and circuit topologies maybe possible.

Similarly, the amplifier 314 of the endpoint device 304 can be formedonto a semiconductor substrate that provides both mechanical support andelectrical connection to the photodiode 310. As with the drive circuit312 of the source device 302, the amplifier 314 of the endpoint device304 can be implemented and/or fabricated in a number of suitable ways.In some examples, the amplifier 314 and the photodiode 310 arefabricated in the same process or operation, but this may not berequired. In some embodiments, the amplifier 314 may be positionedoff-board from a rigid substrate or flexible circuit board to which thephotodiode 310 is coupled. As noted above, it may be appreciated thatthe simplified layout shown in FIG. 3 is merely one example and thatmany other implementations and circuit topologies may be possible.

The source device 302 also includes an optical adapter 316 configured toreflect and/or diverge a laser light beam emitted from the laser diode308, thereby increasing the beam width, divergence angle, and/or beamcross-section by a certain designed amount. In other cases, other beamparameters can be adjusted by the optical adapter 316. In theillustrated embodiment, the optical adapter 316 also redirects the laserlight beam emitted from the laser diode 308 ninety degrees, althoughthis may not be required and/or may vary from embodiment to embodiment.

It may be appreciated, however, that diverging and/or redirecting thebeam output from the laser diode 308 beyond a threshold amount may beundesirable and may contribute to losses. Accordingly, for embodimentsdescribed herein, the optical adapter 316 of the source device 302 istypically configured to modify one or more characteristics of the beamoutput from the laser diode 308 in order to increase positional andangular offset tolerance of the optical communication system withoutincreasing losses beyond a certain selected threshold amount, which mayvary from embodiment to embodiment.

In some embodiments, the optical adapter 316 can be associated with anadjustable optics subsystem of the source device 302. In particular, insome embodiments, the optical adapter 316 can be coupled to an actuationmechanism (not shown) configured to shift and/or tilt the opticaladapter 316 to change and/or tune a direction to which light emitted bythe laser diode 308 propagates. For example, the actuation mechanism ofthe adjustable optics subsystem can move the optical adapter 316 in anysuitable direction relative to the laser diode 308. In otherembodiments, the optical adapter 316 can be tilted relative to the laserdiode 308.

In the illustrated embodiment, the endpoint device 304 can also includean optical adapter 318 configured to reflect and/or concentrate thelaser light beam emitted from the laser diode 308 onto the photodiode310, thereby increasing the quantity of light (e.g., quantity ofphotons) received by the photodiode 310. In the illustrated embodiment,similar to the optical adapter 316 described above, the optical adapter318 also redirects the laser light beam emitted from the laser diode 308ninety degrees, although—as noted above—this may not be required and/ormay vary from embodiment to embodiment. It may be appreciated that, byconcentrating the laser light beam in this manner, the optical adapter318 of the endpoint device 304 also servers to increase positional andangular offset tolerance of the optical communication system. In otherwords, in some embodiments, as a result of the wider area across whichlight is collected by the endpoint device 304, the photodiode 310 of theendpoint device 304 can remain illuminated by the laser light beamemitted from the laser diode 308 even if the endpoint device 304 isoffset from the source device 302 by a small amount.

Similar to the optical adapter 316, the optical adapter 318 can beassociated with an adjustable optics subsystem of the endpoint device304. The optical adapter 318 can be configured in the same mannerdescribed above with respect to the optical adapter 316.

In many embodiments, the optical adapter 316 and the optical adapter 318are made from the same material, but this may not be required. Examplematerials for the optical adapter 316 and the optical adapter 318 caninclude, but may not be limited to flexible or rigid: optically clearpolymers; glass; optically-clear ceramics; plastics; and so on. In somecases, the optical adapter 316 and/or the optical adapter 318 can betreated with an optically reflective outer coating, such as a mirroredor metallic coating. In other cases, other appropriate surface finishesand/or external layers can be added.

Furthermore, although the optical adapter 316 and the optical adapter318 are illustrated as above, and separated from the laser diode 308 andthe photodiode 310, respectively, it may be appreciated that thisconfiguration may not be required of all embodiments. For example, inone embodiment, the optical adapter 316 may be optically coupled to anouter surface of the laser diode 308 via an optically clear adhesive,which may be flexible. More particularly, in some embodiments, theoptically clear adhesive optically coupling the optical adapters 316,318 to the laser diode 308 and the photodiode 310, respectively, mayalso serve as a centering element, at least partially providing arestoring force to the optical adapters 316, 318 in embodimentsincorporating adjustable optics subsystems in either or both theendpoint device 304 or the source device 302.

In this case, the optically clear adhesive may be selected to provide asmooth refractive index transition from the laser diode 308 to theoptical adapter 316; the optically clear adhesive may be selected tohave a refractive index between that of the optical adapter 316 and thelaser diode 308. It may be appreciated that the photodiode 310 and theoptical adapter 318 may be similarly configured.

In other embodiments, additional adapters, lenses, and/or reflectors canbe included. For example, in some embodiments, the optical adapter 316can be optically coupled to the laser diode 308 via a second adapter(e.g., a fiber optic cable). In other cases, one or more lenses (e.g.,concave, convex, Fresnel, and so on) can interpose the laser diode 308and the optical adapter 316. It may be appreciated that the photodiode310 and the optical adapter 318 may be similarly configured.

As noted above, in some embodiments, the source device and the endpointdevice can each include additional and/or alternative opticalstructures—such as optical stabilization subsystems—to increase thequantity of light received by the photodiode of an endpoint device.Generally and broadly, FIGS. 4A-5B each depict various implementationsof an optical stabilization subsystem that can be bodily incorporatedinto either or both source devices and endpoint devices, such asdescribed herein. For simplicity of description, the embodiments thatfollow are described in reference to an example optical stabilizationsubsystem incorporated into an endpoint device, but it may beappreciated that the systems described below can also be incorporatedinto a source device such as described herein.

FIG. 4A depicts an endpoint device 400 of a directional free-spaceoptical communication system. As with other endpoint devices describedherein, the endpoint device 400 includes a photodiode 402 that isdisposed onto and/or coupled (e.g., electrically, mechanically, and soon) to a substrate 404 that can include an amplifier, such as atransimpedance amplifier. The substrate 404 may be flexible or rigid andcan be made from any suitable material or combination or layering ofmaterials. In some embodiments, the substrate 404 is formed, at least inpart, from a semiconductor material.

As noted with respect to other embodiments described herein, theendpoint device 400 of FIG. 4A includes an optical stabilizationsubsystem in order to increase angular and/or positional offsettolerance between the endpoint device 400 and a source device (notshown).

More specifically, the photodiode 402 is positioned below a movable lens406 that is configured to shift in at least one lateral direction. Asthe movable lens 406 changes position, light entering the lens can berepositioned over a photosensitive area of the photodiode 402. In a morespecific example, if laser light enters the movable lens 406 from adirection normal to an outer surface of the photodiode 402, such asshown by the laser light beams u₁ and u₂ of FIG. 4A, repositioning ofthe movable lens 406 may not be required. In other words, light beamsincident ninety degrees from a face of the photodiode 402 may be focusedonto the photosensitive area of the photodiode 402 without any movementor shifting of the movable lens 406.

On the contrary, if laser light enters the movable lens 406 from adirection offset from normal to an outer surface of the photodiode 402,such as shown by the laser light beams u₃ and u₄ of FIG. 4B,repositioning of the movable lens 406 may be preferred. In other words,light beams not incident ninety degrees from a face of the photodiode402 may be repositioned and/or refocused onto the photosensitive area ofthe photodiode 402 by moving, translating, and/or otherwise shifting aposition of the movable lens 406.

To facilitate the movement described above, the movable lens 406 issupported, at least in part, by an actuation mechanism 408. Theactuation mechanism 408 includes at least two supports, identified asthe supports 410, that elevate the movable lens 406 an appropriatedistance above the photodiode 402. The distance by which the supports410 elevate the movable lens 406 may vary from embodiment to embodiment,but it is appreciated that changing the distance between the movablelens 406 and the photodiode 402 may change the extent to which lightentering the movable lens 406 is focused onto the photosensitive area ofthe photodiode 402. In other words, it may be appreciated that thedistance separating the photodiode 402 and the movable lens 406 may varyfrom embodiment to embodiment and/or based on one or morecharacteristics of the movable lens 406 (e.g., radius of curvature,focal length, shape, and so on) or one or more characteristics of thephotodiode 402 (e.g., size and/or area of the photosensitive area,height of the photodiode 402, and so on). In some embodiments, thedistance between the movable lens 406 and the photodiode 402 is fixed,although this may not be required; in other embodiments, the distancebetween the photodiode 402 and the movable lens 406 can be dynamicallyadjusted.

The actuation mechanism 408 also includes one or more electromagnets,identified as the electromagnets 412, that can be selectively actuatedto attract and/or repel the movable lens 406 (see, e.g., FIG. 4B). Morespecifically, the electromagnets 412 are positioned so as to attract orrepel permanent magnets (or, in alternative embodiments, additional orauxiliary electromagnets) disposed and coupled to a periphery of themovable lens 406. Two example permanent magnets are identified in FIGS.4A-4B as the permanent magnets 414.

In typical examples, the optical stabilization subsystem also includes acontroller that, in some cases, can be formed into and/or otherwisecoupled to the substrate 404. The controller, as noted above, isconfigured to apply one or more electrical signals to the actuationmechanism 408—or, more specifically, to the electromagnets 412 of theactuation mechanism 408—in order to control movement of the movable lens406 in particular directions and by particular amounts.

More specifically, in the illustrated example, the controller of theoptical stabilization subsystem can be configured to control electricalcurrent applied to the electromagnets 412, thereby causing theelectromagnets 412 to each generate a corresponding magnetic fieldhaving a specific magnitude and polarity. By controlling the polarityand amplitude of current applied to each of the electromagnets 412, thecontroller can effectively control the magnetic fields generated by theelectromagnets 412 and, in turn, control the amount or extent to whichthe magnetic fields generated by the electromagnets 412 attract or repelthe permanent magnets 414. In some examples, the controller can applycurrent to only one electromagnet at a time, whereas in other examplesthe controller applies current to multiple electromagnets at the sametime.

The controller can be a processor, digital circuit, analog circuit, orany combination thereof. In many examples, the controller can becommunicably coupled to one or more sensors of the optical stabilizationsubsystem, the endpoint device 400, or a sensor in communication withthe endpoint device 400. In these examples, the controller can beconfigured to move the movable lens 406 in response to receiving inputfrom a sensor (or more than one sensor).

For example, in one embodiment, the endpoint device 400 includes aninertial sensor, such as a gyroscopic sensor (also referred to as anangular rate or angular velocity sensor). The inertial sensor can beconfigured to monitor for, and report, movement of the endpoint device400. In response to a movement of the endpoint device 400 reported bythe inertial sensor, the controller of the optical stabilizationsubsystem can be configured to adjust the position of the movable lens406 to counteract the movement of the endpoint device 400 insubstantially real time. For example, if the inertial sensor reportsthat endpoint device 400 has shifted to the right of the page as shownin FIGS. 4A-4B, the controller of the optical stabilization subsystemcan cause the actuation mechanism 408 to move the movable lens 406 tothe left of the page as shown in FIG. 4B, thereby counteracting thereported movement of the endpoint device 400.

In many examples, the actuation mechanism 408 also includes a centeringelement 416. As noted with respect to other embodiments describedherein, the centering element 416 can serve to provide a restoring forcethat resists changes in position of the movable lens 406 caused by theactuation mechanism 408. In the illustrated embodiment, the centeringelement 416 is a mechanical spring; although this is merely one example.In other embodiments, the centering element 416 may be implemented inanother manner. Example centering elements include, but are not limitedto: elastomers; leaf springs; spiral springs; flexion rods; and so on.

The foregoing embodiment depicted in FIGS. 4A-4B is merely one exampleconstruction of an optical stabilization subsystem such as describedherein. As such, it may be appreciated that an optical stabilizationsubsystem can be configured in a manner different than shown. Regardlessthe particular construction selected for a particular implementation, itmay be appreciated that incorporating an optical stabilization subsysteminto either or both a source device or an endpoint device of adirectional free-space optical communication system, such as describedherein, can increase angular and positional offset tolerance between thesource device and the endpoint device, thereby improving the range,reliability, and speed of communication between the two devices.

Furthermore, it is appreciated that the single degree of freedomconstruction, as depicted in FIGS. 4A-4B, is merely one example. Inother embodiments, an actuation mechanism of an optical stabilizationsubsystem can be configured to shift a movable lens (and/or movablereflector) in any suitable direction. For example, in some embodiments,an actuation mechanism can include four electromagnets disposed atninety-degree intervals around a perimeter or periphery of a movablelens. Each of the four electromagnets can be positioned relative to apermanent magnet coupled to the movable lens. In this example, acontroller of the optical stabilization subsystem can be configured toapply current to one or more of the four electromagnets in order to movethe movable lens in two dimensions. In other cases, an actuationmechanism can include a different number of electromagnet/permanentmagnet pairs.

In still further examples, an actuation mechanism, such as describedherein, may be configured to operate without generating magnetic fields.Non-magnetic actuation mechanisms that may be appropriately incorporatedinto an optical stabilization subsystem, such as described hereininclude, but are not limited to: electrostatic attraction mechanisms;piezoelectric mechanisms; pressure bladder mechanisms; microscopicelectromechanical actuators; electroactive polymer mechanisms;shape-memory alloy mechanism; and so on. In some cases, a centeringelement can also serve to move the movable lens. For example, thecentering element may be a spring formed from a shape memory alloy; whensupplied with current, the centering element changes shape, changing theposition of the movable lens in one or more directions. When the supplyof current is terminated, the movable lens can return to a centralposition.

In still further embodiments, an actuation mechanism may be configuredto tilt a movable lens (and/or a photodiode or laser diode below thelens) in addition to—or as an alternative to—laterally shifting themovable lens, such as described above in reference to FIGS. 4A-4B.

FIG. 5A depicts an endpoint device 500 of a directional free-spaceoptical communication system including an optical stabilizationsubsystem. The endpoint device 500 includes a photodiode 502 and asubstrate 504. The photodiode 502 (and, additionally, an amplifier suchas described in reference to other embodiments describe herein) ispositioned below, and aligned with, a lens 506. The lens 506 and thephotodiode 502 are supported by an actuation mechanism 508 that includesa pivoting frame 510. The pivoting frame 510 pivots over a fulcrum point512 toward or away from a support 514. A centering element 516 isdisposed between the pivoting frame 510 and the support 514 to provide arestoring force that resists changes in position (e.g., angle) of thepivoting frame 510 (see, e.g., FIG. 5B). In this embodiment, acontroller of the optical stabilization subsystem can be configured toprovide a signal to the actuation mechanism 508 to cause the actuationmechanism 508 to tilt the pivoting frame 510 in a particular direction.In one example, the actuation mechanism can include electromagnets andpermanent magnets such as described above in reference to FIGS. 4A-4B.

It may be appreciated that the foregoing description of FIGS. 4A-5B, andthe various alternatives thereof and variations thereto are presented,generally, for purposes of explanation, and to facilitate a thoroughunderstanding of various possible configurations of an adjustable opticssubsystem in an endpoint device or source device of a directionalfree-space optical communication system, such as described herein.However, it will be apparent to one skilled in the art that some of thespecific details presented herein may not be required in order topractice a particular described embodiment, or an equivalent thereof.

Thus, it is understood that the foregoing descriptions of specificembodiments are presented for the limited purposes of illustration anddescription. These descriptions are not exhaustive nor intended to limitthe disclosure to the precise forms recited herein. To the contrary, itwill be apparent to one of ordinary skill in the art that manymodifications and variations are possible in view of the aboveteachings.

For example, a controller of an adjustable optics subsystem can beconfigured to move and/or tilt a movable lens in response to anyappropriate stimulation. For example, a controller of an adjustableoptics subsystem in an endpoint device of a directional free-spaceoptical communication system can be configured to monitor power outputfrom the photodiode of the endpoint device to determine whether lightreceived on the photosensitive area of the photodiode is appropriatelypositioned on the photosensitive area. For example, FIG. 6A depicts atop view of a photodiode 600 of an endpoint device of a directionalfree-space optical communication system. The photodiode 600 is disposedin a component enclosure that defines an exterior surface 602 thatdefines a photosensitive area illustrated as the central portion 604 ofthe exterior surface. The central portion 604 is defined in thegeometric center of the exterior surface 602, surrounded by a partition606 (acting as an aperture) formed from metal. The partition 606separates the central portion 604 from the remaining portion of thephotosensitive area such that the remaining portion of thephotosensitive area surrounds the central portion 604, separated by thepartition 606. In some cases, the photodiode 600 can include a partitionformed from another material such as plastic, ink, glass, and so on;metal may not be required for all embodiments and the partition 606 ismerely one example.

As a result of this construction, a focused beam 608 that is notproperly positioned/aligned in the central portion 604 (see, e.g., FIG.6B) of the photosensitive area can at least partially illuminate thepartition 606, causing power output from the central portion 604 tofall. Once the controller of the adjustable optics subsystem recognizesthat power output from the central portion 604 of the photodiode 600 hasdropped beyond a threshold value, it can instruct an actuation mechanismto move the movable lens in order to re-center the focused beam 608relative to the central portion 604 (see, e.g., FIG. 6A).

As noted with respect to other embodiments described herein, thecontroller of the adjustable optics subsystem can move the movable lensin any suitable manner, following any suitable technique. In oneexample, once a drop in power is detected, the controller of theadjustable optics subsystem can instruct the movable lens to move in apre-defined pattern, such as a cross pattern. As the movable lens ismoved, the controller can monitor power output from the photodiode todetermine a location of the movable lens that corresponds to the highestpower output. In the case that more than one location of the movablelens corresponds to high power output, an average location (e.g.,geometric center of mass of the multiple high-power locations) may beused if the output at that location is above a threshold value. In stillother embodiments, the controller of the adjustable optics subsystem canimplement a maximization algorithm to determine the coordinate locationof the movable lens corresponding to maximum power output from thephotodiode. Suitable algorithms can include: watershed algorithms;gradient ascent/descent algorithms; segmentation algorithms; and so on.It may be appreciated that any technique and/or combination oftechniques can be used by the controller to determine a position for amovable lens.

In some examples, the controller of the adjustable optics subsystem cancontinually operate in a feedback loop in order to continually adjustthe position of the movable lens. Feedback can be received by thecontroller from any suitable feedback source including, withoutlimitation: inertial sensors; positional sensors; data or informationfrom a source device or endpoint device; output from an optimizationalgorithm; output power from the central region of the photodiode and/orouter region of the photodiode; and so on.

In other cases, the controller of the adjustable optics subsystem can beconfigured to adjust the position of the movable lens at a particulartime (e.g., interval, scheduled time or date, and so on) or in responseto a particular trigger. For example, the controller of the adjustableoptics subsystem can be configured, in one embodiment, to adjust theposition of the movable lens only in response to a request to send orreceive data using the directional free-space optical communicationsystem. In other cases, other triggers can be received by the controllerincluding, but not limited to: user input; data or information receivedfrom a communication channel different from the directional free-spaceoptical communication system (e.g., Wi-Fi, Bluetooth, Near-Fieldcommunication, Ethernet, and so on); data or information received viathe directional free-space optical communication system; and so on.

In some cases, an adjustable optics subsystem in a source device of adirectional free-space optical communication system can cooperate withan adjustable optics subsystem in an endpoint device of the same system.For example, both devices can be placed in a pairing or linking mode.When in the pairing or linking mode, the adjustable optics subsystem inthe source device can cause the movable lens to scan in a particulardirection or according to a particular scanning pattern and/orpredefined pattern (e.g., line-scan vertically and/or horizontally). Insome embodiments, when in the pairing or linking mode, the movable lensin the source device is moved at a first, high speed.

While the adjustable optics subsystem in the source device is scanning,the adjustable optics subsystem in the endpoint device may be static ormay scan at a lower rate than the adjustable optics subsystem in thesource device, monitoring power output from the photodiode for anincrease in power. Once an increase in power is detected, the endpointdevice can signal the source device using an appropriate communicationprotocol or technique to stop scanning. In some cases, a timestamp canbe sent to the source device, but this may not be required.

In other cases, the signal from the endpoint device may cause the sourcedevice to scan at a second, lower rate or speed within a particularangular range based on, in some examples, the time at which the sourcedevice received the signal to stop scanning from the endpoint device.Thereafter, once the adjustable optics subsystem in the source devicehas determined a position for the movable lens, the adjustable opticssubsystem in the endpoint device can begin moving the movable lens inaccordance with one or more techniques described herein. In this manner,the adjustable optics subsystem in the source device and the adjustableoptics subsystem in the endpoint device cooperate to increase angularand/or positional offset tolerance between the two devices.

Still further embodiments can be configured in a different manner. Forexample, as shown in FIG. 6C, in some examples, the partition 606 can bethin, relative to the expected cross-sectional area of the focused beam608.

As a result of this construction, a focused beam 608 that is notproperly positioned/aligned in the central portion 604 of thephotosensitive area can at least partially illuminate the remainingportion of the photosensitive area of the photodiode 600, causing poweroutput from the central portion 604 to fall and causing power outputfrom the remaining portion to increase. Once the controller of theadjustable optics subsystem recognizes that power output from thecentral portion 604 of the photodiode 600 has dropped beyond a thresholdvalue and/or that power output from the remaining portion has increased,it can instruct an actuation mechanism to move the movable lens in orderto re-center the focused beam 608 relative to the central portion 604(see, e.g., FIG. 6A).

In still further examples, the remaining portion of the photosensitivearea can be segmented. For example, FIG. 7 depicts a photodiode 700that, like the embodiments depicted in FIGS. 6A-6C, includes an exteriorsurface 702 that defines a photosensitive area. A central portion 704 ofthe photosensitive area is defined in the geometric center of theexterior surface 702, surrounded by a partition 706 formed from amaterial such as metal. The partition 706 separates the central portion704 from the remaining portion of the photosensitive area. In thisembodiment, the remaining portion of the photosensitive area ispartitioned, segmented, and/or otherwise separated into four discreteregions evenly distributed around the periphery/perimeter of thepartition 706, labeled as the segments 702 a-702 d of the remainingportion of the photosensitive area. In particular, the remaining portionof the photosensitive area is partitioned by a metal mask 710.

As a result of this construction, a focused beam 708 that is notproperly positioned/aligned in the central portion 704 of thephotosensitive area can at least partially illuminate at least onesegment 702 a-702 d of the remaining portion of the photosensitive areaof the photodiode 700, causing power output from the central portion 704to fall and causing power output from the illuminated segment(s) toincrease. Once the controller of the adjustable optics subsystemrecognizes that power output from the central portion 704 of thephotodiode 700 has dropped beyond a threshold value and/or that poweroutput from the remaining portion has increased, it can instruct anactuation mechanism to move the movable lens in order to re-center thefocused beam 708 relative to the central portion 704 (see, e.g., FIG.6A). In this example, re-centering movement of the movable lens may beperformed proportionality based on which of the segment(s) 702 a-702 dare illuminated. For example, if the segment 702 b is illuminated, butnone of the other segments are illuminated, the controller of theadjustable optics subsystem can cause the movable lens to changeposition such that the focused beam 708 moves diagonally toward thesegment 702 d. Similarly, if the segment 702 b is illuminated along withthe segment 702 a, but neither of the other two segments is illuminated,the controller of the adjustable optics subsystem can cause the movablelens to change position such that the focused beam 708 moveshorizontally toward the left of the figure.

It may be appreciated that four segments, such as shown, is merely oneexample. Other embodiments can include a greater or less number ofsegments, segment patterns or distributions, and so on. Further, inother embodiments, the distribution of segments may not be uniform; insome cases, segments along horizontal regions of a photodiode may have asmaller area than segments along vertical regions of the photodiode.

It may be appreciated that the foregoing description of FIGS. 6A-7, andthe various alternatives thereof and variations thereto are presented,generally, for purposes of explanation, and to facilitate a thoroughunderstanding of various possible configurations of an adjustable opticssubsystem in an endpoint device or source device of a directionalfree-space optical communication system, such as described herein.However, it will be apparent to one skilled in the art that some of thespecific details presented herein may not be required in order topractice a particular described embodiment, or an equivalent thereof.

Thus, it is understood that the foregoing descriptions of specificembodiments are presented for the limited purposes of illustration anddescription. These descriptions are not exhaustive nor intended to limitthe disclosure to the precise forms recited herein. To the contrary, itwill be apparent to one of ordinary skill in the art that manymodifications and variations are possible in view of the aboveteachings.

Generally and broadly, FIGS. 8-9 depict simplified flow chartscorresponding to various ordered and/or unordered operations of methodsthat may be used to manufacture one or more components such as describedherein. It may be appreciated that these simplified examples may bemodified in a variety of ways. In some examples, additional,alternative, or fewer operations than those depicted and described maybe possible.

FIG. 8 is a simplified flow chart showing example operations of a methodof positioning a movable lens in a directional free-space opticalcommunication system, such as described herein.

The method 800—which can be performed by one or more controllers of anadjustable optics subsystem, such as described herein—includes operation802 in which at least one of a source device or an endpoint device of adirectional free-space optical communication system, such as describedherein, enters a link mode. At operation 804, a power output (or othersuitable output or characteristic, such as voltage, current, orresistance) of a photosensitive element or photodetector is measured. Asnoted with respect to embodiments described herein, the photosensitiveelement is typically disposed within an endpoint device. Next, atoperation 806, a lens positioned above the photodetector is adjusted, ifnecessary. Finally, at operation 808, a communication link between theendpoint device and the source device can be established via appropriatehandshake and/or negotiation. In other words, the device(s) may exit thelink mode and may proceed to exchange data or information via thedirectional free-space optical communication system by entering acommunication mode or a data transfer mode.

In many cases, a directional free-space optical communication systemincludes two devices that each can function as a source device and anendpoint device. In these examples, the method 800 can be performed byboth communicated devices, either simultaneously or otherwise, in orderto ensure that the photodiode of one device is appropriately alignedwith the laser diode of the other device and vice versa.

FIG. 9 is a simplified flow chart showing example operations of anothermethod of positioning a movable lens in a directional free-space opticalcommunication system, such as described herein. The method 900 begins atoperation 902 in which data is received at an endpoint device from asource device of an optical communication system. Next, at operation904, an error can be detected that corresponds to an angular offsetbetween the source device and the endpoint device. As described above,the error can be detected based on a received power drop detected in theendpoint device. Next, at operation 906, a position of a movable lens inthe endpoint device can be adjusted to maximize power output. The methodthen continues back to operation 904. In other embodiments, a movablelens in an endpoint device can be moved based on historical or recentposition information. In some embodiments, a movable lens can be movedbased on a predicted future location of a source device (e.g., aprediction based on an estimation algorithm, such as a Kalman filter).

In some cases, an angular error detected at operation 904 cannot becorrected by operation 906. In these cases, an endpoint device maygenerate a notification to a user and/or to the source device that thecommunication link between the source device and the endpoint device hasbeen broken.

In many cases, a directional free-space optical communication systemincludes two devices that each can function as a source device and anendpoint device. In these examples, the method 900 can be performed byboth communicated devices, either simultaneously or otherwise, in orderto ensure that the photodiode of one device is appropriately alignedwith the laser diode of the other device and vice versa.

One may appreciate that, although many embodiments are disclosed above,the operations and steps presented with respect to methods andtechniques described herein are meant as exemplary and accordingly arenot exhaustive. One may further appreciate that alternate step order orfewer or additional operations may be required or desired for particularembodiments.

Although the disclosure above is described in terms of various exemplaryembodiments and implementations, it should be understood that thevarious features, aspects and functionality described in one or more ofthe individual embodiments are not limited in their applicability to theparticular embodiment with which they are described, but instead can beapplied, alone or in various combinations, to one or more of the someembodiments of the invention, whether or not such embodiments aredescribed and whether or not such features are presented as being a partof a described embodiment. Thus, the breadth and scope of the presentinvention should not be limited by any of the above-described exemplaryembodiments but are instead defined by the claims herein presented.

What is claimed is:
 1. An apparatus for free-space optical communicationcomprising: a substrate; a photosensitive element coupled to thesubstrate and comprising: a first photosensitive area; and a secondphotosensitive area; a movable lens above the photosensitive element;and a controller coupled to the movable lens and configured to adjust aposition of the movable lens based on a first power output from thefirst photosensitive area and a second power output from the secondphotosensitive area.
 2. The apparatus of claim 1, wherein the firstphotosensitive area is positioned in a geometric center of an exteriorsurface of the photosensitive element.
 3. The apparatus of claim 2,wherein the second photosensitive area surrounds the firstphotosensitive area.
 4. The apparatus of claim 1, wherein the secondphotosensitive area is segmented.
 5. The apparatus of claim 4, whereinthe second photosensitive area includes at least three segments.
 6. Theapparatus of claim 5, wherein: the second power output is from a firstsegment of the at least three segments of the second photosensitivearea; and the controller is configured to adjust the position of themovable lens based on a third power output from a second segment of theat least three segments of the second photosensitive area.
 7. Theapparatus of claim 1, wherein the controller is configured to adjust theposition of the movable lens in response to an increase in the secondpower output and a decrease in the first power output.
 8. The apparatusof claim 1, wherein the first photosensitive area and the secondphotosensitive area are separated by a partition formed from metal.
 9. Asystem for free-space optical communication comprising: a firstapparatus comprising: a light source; a first movable lens above thelight source; and a first controller configured to adjust a firstposition of the first movable lens in a pattern; and a second apparatuscomprising: a photosensitive element comprising: a first photosensitivearea; and a second photosensitive area; a second movable lens above thephotosensitive element; and a second controller configured to adjust asecond position of the second movable lens based on changes in poweroutput from the first photosensitive area and the second photosensitivearea.
 10. The system of claim 9, wherein: the light source comprises avertical-cavity surface-emitting laser; and the photosensitive elementcomprises a photodiode.
 11. The system of claim 9, wherein the secondcontroller is configured to adjust the second position of the secondmovable lens after the first controller stops scanning.
 12. The systemof claim 9, wherein the second controller is configured to tilt thesecond movable lens.
 13. The system of claim 12, wherein the secondcontroller is configured to tilt the photosensitive element with thesecond movable lens.
 14. The system of claim 9, wherein the secondcontroller is configured to shift the second movable lens laterally. 15.The system of claim 9, wherein: the first photosensitive area iscircular; and the second photosensitive area surrounds the firstphotosensitive area.
 16. The system of claim 15, wherein the secondphotosensitive area is segmented.
 17. A method of operating a free-spaceoptical communication system comprising a source device and an endpointdevice, the method comprising: changing a first position of a firstmovable lens according to a pattern, the first movable lens positionedover a laser diode in the source device; monitoring a first power outputfrom at least one photosensitive area of a photodiode in the endpointdevice; in response to the first power output crossing a firstthreshold, sending a signal to the source device to stop changing thefirst position of the first movable lens; changing a second position ofa second movable lens positioned over the photodiode; monitoring asecond power output from at least one photosensitive area of thephotodiode; and in response to the second power output crossing a secondthreshold, stopping movement of the second movable lens.
 18. The methodof claim 17, wherein the pattern is predefined.
 19. The method of claim17, wherein changing the first position of the first movable lens isperformed, at least in part, by a controller of an adjustable opticssubsystem in the source device.
 20. The method of claim 17, furthercomprising entering a data transfer mode by the source device and theendpoint device after stopping movement of the second movable lens.